1. Field of the Invention
The present invention relates to a magnetic card recording apparatus so designed that information is recorded with a predetermined high recording density on a magnetic card moving at a varying speed.
2. Description of the Prior Art
Magnetic cards made of a plastic material or a paper coated with a magnetic material have recently been used as bank cards, credit cards, gasoline station service cards or the like.
These magnetic cards have been mainly adapted for the purpose of reading, and it has been a usual practice to effect the writing of information on the cards collectively at an issuing center or the like. The reason is that, since the magnetic card must be moved at a constant speed in order to record information on the magnetic card with a constant recording density, many of the recording apparatuses are of the type in which the magnetic card is moved at a constant speed by an electric motor or the like and thus the apparatus become large in size and high in cost.
Another type of apparatus is known in which the magnetic card is moved manually and the movement of the magnetic card is sensed by a sensor which is rotated in response to the movement of the magnetic card to generate pulses proportional to its rotational speed, thus recording information on the card by using the pulses. Still another recording apparatus of manual type is known in which clock signals are recorded beforehand along one of the recording tracks on the magnetic card such that the clock signals are read and used as writing clock signals to record information on the card.
The type of apparatus in which the magnetic card is moved by an electric motor has the disadvantage to become large in size, complicated in construction and high in cost. Another apparatus of the type employing a rotary or sliding sensor so as to generate pulses of a frequency proportional to the moving speed of a magnetic card is also disadvantageous in that the generated pulse frequency is limited by the construction of the pulse sensor used.
As a rule, the recording of information with a high recording density requires the use of pulses having a high frequency. Conventionally, a type of sensor has been used as a highly accurate method, in which a round or long plate is provided with slits and a light source and a photo sensor are arranged facing the slits so as to sense a light signal passing through the slit. However, there is a physical limitation to the provision of slits, and thus it is difficult to generate high-frequency pulses. Another disadvantage is that, in order to generate desired high-frequency pulses, the movement of the pulse sensor must be mechanically amplified in relation to the amount of movement of the card, thus making the apparatus not only complicated in construction but also large in size.
The apparatus of the type in which a clock signal recorded beforehand along one of the recording tracks on a magnetic card is read and an information signal is recorded along another track in synchronism with the clock signal read, is disadvantageous in that not only the recording capacity is decreased by the use of one of the tracks exclusively for the purpose of recording the clock signal but also there is a problem of the occurrence of cross-talk between the channels of the magnetic head due to the recording performed while reading the clock signal, thus placing limitations on the recording system and the recording density in view of the necessity of overcoming the problem of cross-talk. Moreover, the recent developments in the standardization of magnetic cards have made it necessary to record information on a plurality of recording tracks of the card with different recording densities, thus making it difficult to use one of the recording tracks exclusively for the purpose of recording the clock signal.